Substrate processing apparatus

ABSTRACT

A substrate processing apparatus, for generating a plasma from a gas by a high frequency energy and etching a substrate in a processing chamber by radicals in the plasma, includes a high frequency power supply configured to supply the high frequency energy into the processing chamber, a gas supply source configured to introduce the gas into the processing chamber, a mounting table configured to mount the substrate thereon, and a partition plate provided in the processing chamber and configured to divide an inner space of the processing chamber into a plasma generation space and a substrate processing space and suppress passage of ions therethrough. The partition plate and a portion of an inner wall surface of the processing chamber which is positioned at least above the mounting table are covered by a dielectric material having a recombination coefficient of 0.002 or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/449,675, filed on Mar. 3, 2017, now U.S. Pat.No. 10,734,201, which claims priority to Japanese Patent Application No.2016-042010 filed on Mar. 4, 2016, the entire contents each applicationare incorporated herein by reference.

FIELD OF THE INVENTION

The disclosure relates to a substrate processing apparatus.

BACKGROUND OF THE INVENTION

There has been suggested a method for etching a semiconductor wafer(hereinafter, referred to as “wafer”) in a processing chamber mainly byradicals in a plasma (see, e.g., PCT Publication No. 2013/175897). Inthe case of etching the wafer mainly by radicals, action of ions in theplasma on the wafer may need to be suppressed. Therefore, a partitionplate for dividing an inner space of the processing chamber into aplasma generation space and a substrate processing space is providedinside the processing chamber. The partition plate suppresses passage ofions in the plasma from the plasma generation space to the substrateprocessing space.

On the other hand, the radicals in the plasma pass through the partitionplate to reach the substrate processing space and contribute to theetching of the wafer. Therefore, the etching using radicals can beperformed while suppressing approach of ions to the surface of thewafer. At this time, since the radicals reach the surface of the waferwithout inactivation, an etching rate is increased. Accordingly, theetching process can be promoted. The inactivation of the radicalsindicates that the radicals lose activity.

When the radicals are diffused and adsorbed onto the inner wall surfaceof the processing chamber and the components in the processing chamber,the adsorbed radicals are inactivated. Especially, when a distancebetween the wafer provided in the processing chamber and the inner wallof the processing chamber is short, it is easy for the radicals to beadsorbed onto the inner wall of the processing chamber, and the amountof inactivated radicals is increased. Thus, an etching rate becomeslower at an outer peripheral side than at an inner peripheral side ofthe wafer. Accordingly, in-plane uniformity of the etching deteriorates.

SUMMARY OF THE INVENTION

In view of the above, the disclosure provides a technique forsuppressing inactivation of radicals and achieving uniformity ofetching.

In accordance with an aspect, there is provided a substrate processingapparatus for generating a plasma from a gas by a high frequency energyand etching a substrate in a processing chamber by radicals in theplasma, including: a high frequency power supply configured to supplythe high frequency energy into the processing chamber; a gas supplysource configured to introduce the gas into the processing chamber; amounting table configured to mount the substrate thereon; and apartition plate provided in the processing chamber and configured todivide an inner space of the processing chamber into a plasma generationspace and a substrate processing space and suppress passage of ionstherethrough, wherein the partition plate and a portion of an inner wallsurface of the processing chamber which is positioned at least above themounting table are covered by a dielectric material having arecombination coefficient of 0.002 or less.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the disclosure will become apparent from thefollowing description of embodiments, given in conjunction with theaccompanying drawings, in which:

FIG. 1 shows an example of a substrate processing system including aradical processing apparatus according to an embodiment;

FIG. 2 is a vertical cross sectional view showing an example of theradical processing apparatus according to the embodiment;

FIGS. 3 and 4 show recombination probabilities of radicals on surfaces;and

FIGS. 5A and 5B show examples of an etching result obtained by using theradical processing apparatus according to the embodiment and an etchingresult of a comparative example.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described with reference to theaccompanying drawings. Like reference numerals will be used forsubstantially like parts throughout the specification and the drawings,and redundant description thereof will be omitted.

(Configuration of Substrate Processing System)

First, a substrate processing system including a radical processingapparatus according to an embodiment will be described with reference toFIG. 1. The radical processing apparatus is an example of a substrateprocessing apparatus.

A substrate processing system 1 of the present embodiment includes aloader module 2, two load-lock chambers 3, two PHT (Post Heat Treatment)processing apparatuses 4, and two radical processing apparatuses 5. Theloader module 2 allows loading/unloading of a wafer W that is an exampleof an unprocessed substrate. The two load-lock chambers 3 are providedadjacent to the loader module 2. The PHT processing apparatuses 4 areprovided adjacent to the respective load-lock chambers 3. Each of thePHT processing apparatuses 4 performs PHT on the wafer W. The radicalprocessing apparatuses 5 are provided adjacent to the respective PHTprocessing apparatuses 4. Each of the radical processing apparatuses 5performs radical processing on the wafer W.

The load-lock chamber 3, the PHT processing apparatus and the radicalprocessing apparatus 5 are arranged linearly in that order. The PHTprocessing apparatus 4 and the radical processing apparatus 5 areconfigured to process wafers W one by one. However, the PHT processingapparatus 4 and the radical processing apparatus 5 may process twowafers W at a time.

The loader module 2 includes a transfer chamber 12 where a first wafertransfer unit 11 for transferring the wafer W is provided. The firstwafer transfer unit 11 has two transfer arms 11 a and 11 b forsubstantially horizontally supporting the wafer W. A stage 13 isprovided at a longitudinal side of the transfer chamber 12. For example,three carriers C, each capable of accommodating a plurality of wafers W,can be connected to the stage 13. An orienter for performing positionalignment by by rotating the wafer W to optically obtain eccentricity isprovided near the transfer chamber 12.

In the loader module 2, the wafer W is held by the transfer arm 11 a or11 b. The first wafer transfer unit 11 can transfer the wafer W to adesired position by linearly moving the wafer W in a substantiallyhorizontal plane and vertically moving the wafer W. The wafer W isloaded into and unloaded from the carriers C on the stage 13, theorienter 14, and the load-lock chambers 3 by the extension andretraction of the transfer arm 11 a or 11 b.

Each of the load-lock chambers 3 is connected to the transfer chamber 12through a gate valve 16. A second wafer transfer unit 17 fortransferring the wafer W is provided in each of the load-lock chambers3. The load-lock chambers 3 can be evacuated to a predetermined vacuumlevel.

The second wafer transfer unit 17 has a multi-joint arm structure and apick for substantially horizontally holding the wafer W. In the secondwafer transfer unit 17, the pick is positioned in the load-lock chamber3 when the arm is retracted. The pick reaches the PHT processingapparatus 4 when the arm is extended. The pick can reach the radicalprocessing apparatus 5 when the arm is further extended. Therefore, thewafer W can be transferred between the load-lock chamber 3, the PHTprocessing apparatus 4 and the radical processing apparatus 5.

The PHT processing apparatus 4 includes a vacuum evacuable processingchamber 20 and a mounting table 23 for horizontally mounting thereon thewafer W in the processing chamber 20. A heater is embedded in themounting table 23. By heating the wafer W that has been subjected to theradical processing by the heater, PHT processing for vaporizing reactionby-products generated by the radical processing is performed. During thePHT processing, an inert gas such as N₂ gas or the like is introducedinto the processing chamber 20. A gate valve 22 is provided at a side ofthe processing chamber 20 which faces the load-lock chamber 3. A gatevalve 54 is provided at a side of the processing chamber 20 which facesthe radical processing apparatus 5.

The radical processing apparatus 5 of the present embodiment performsthe radical processing on an oxide film on the surface of the wafer Wmounted on a mounting table 41 in a processing chamber 40 by using afluorine-containing gas and a hydrogen-containing gas (e.g., NH₃). Inother words, radicals obtained by activating the fluorine-containing gasare used. The radical processing apparatus 5 may also be applied to thecase of etching a nitride film such as a silicon nitride film (SiN) orsilicon (Si) by using radicals obtained by activating a gas containingat least fluorine. The radical processing apparatus 5 may also beapplied to the case of etching a metal film by using radicals obtainedby activating a gas containing at least chlorine.

A control unit 90 includes a process controller 91 having amicroprocessor (computer) for controlling the respective components ofthe substrate processing system 1. The process controller 91 isconnected to a user interface including a keyboard through which anoperator inputs commands to manage the substrate processing system 1, adisplay for visualizing and displaying an operation state of thesubstrate processing system 1, and the like. The process controller 91is also connected to a storage unit 93 which stores control programs forrealizing various processes performed in the substrate processing system1, e.g., the supply of the processing gas in the radical processingapparatus 5, the exhaust of the processing chamber 40 and the like,under the control of the process controller 91, processing recipes thatare control programs for allowing the respective components of thesubstrate processing system 1 to perform predetermined processes basedon processing conditions, various database and the like. The recipes arestored in an appropriate storage medium (not shown) in the storage unit93. If necessary, any recipe is read out from the storage unit 93 andexecuted in the process controller 91. Accordingly, a desired process inthe substrate processing system 1 is performed under the control of theprocess controller 91.

(Operations of the Substrate Processing System)

Hereinafter, processing operations in the substrate processing system 1configured as described above will be described. First, wafers W, eachhaving on a surface thereof a silicon oxide film, are transferred to thesubstrate processing system 1 while being accommodated in a carrier C.In the substrate processing system 1, in a state where the gate valve 16of an atmospheric side is opened, a wafer W is transferred from thecarrier C of the loader module 2 to the load-lock chamber 3 and thendelivered to the pick of the second wafer transfer unit 17 in theload-lock chamber 3 by one of the transfer arms 11 a and 11 b of thefirst wafer transfer unit 11.

Next, the load-lock chamber 3 is vacuum-evacuated by closing the gatevalve 16 of the atmospheric side. Then, the gate valves 22 and 54 areopened, and the wafer W is transferred to the radical processingapparatus 5 by extending the pick to the radical processing apparatus 5.Thereafter, the pick is returned to the load-lock chamber 3 and the gatevalves 22 and 54 are closed. Then, the radical processing is performedin the radical processing apparatus 5. In the radical processing, afluorine-containing gas, a hydrogen-containing gas (e.g., NH₃), and anSiO₂ film formed on the surface of the wafer W react with each other togenerate ammonium hexafluorosilicate (AFS) that can be decomposed byheat.

Upon completion of the radical processing, the gate valves 22 and 54 areopened, and the processed wafer W is received by the pick of the secondwafer transfer unit 17 and mounted on the mounting table 41 of theprocessing chamber 40 of the PHT processing apparatus 4. Then, the pickis retracted to the load-lock chamber 3, and the gate valves 22 and 54are closed. Thereafter, PHT processing is performed by heating the waferW in the processing chamber 40 of the PHT processing apparatus 4.Accordingly, reaction by-products of AFS generated by the radicalprocessing are sublimated by the heating and removed.

Upon completion of the heat treatment in the PHT processing apparatus 4,the gate valve 22 is opened and the etched wafer W on the mounting table23 is retreated to the load-lock chamber 3 by the pick of the secondwafer transfer unit 17 and then returned to the carrier C by any one ofthe transfer arms 11 a and 11 b of the first wafer transfer unit 11. Inthis manner, processing of a single wafer is completed. The above seriesof operations are repeated for all the wafers W accommodated in thecarrier C.

(Configuration of Radical Processing Apparatus)

Hereinafter, the radical processing apparatus 5 of the presentembodiment will be described. FIG. 2 is a cross sectional view showingan example of the radical processing apparatus of the presentembodiment. The radical processing apparatus 5 includes the processingchamber 40 having an airtight structure. The processing chamber 40 ismade of, e.g., aluminum or aluminum alloy, and has an open top. The opentop is blocked by a cover 52 serving as a ceiling portion. Aloading/unloading port (not shown) through which the wafer W istransferred to and from the PHT processing apparatus 4 is provided at asidewall 40 a of the processing chamber 40. The loading/unloading portcan be opened and closed by the gate valve 54 shown in FIG. 1.

Provided in the processing chamber 40 are the mounting table 41 forhorizontally mounting thereon a single wafer W, and an elevation unit 45for vertically moving the mounting table 41.

The mounting table 41 is formed in a substantially columnar shape. Themounting table 41 includes a mounting plate 61 having a mounting surfacefor the wafer W and a base block 62 for supporting the mounting plate61. A temperature control unit 63 for controlling a temperature of thewafer W is provided in the mounting plate 61. The temperature controlunit 63 includes a conduit through which a temperature control medium(e.g., water or the like) circulates. The temperature of the wafer W iscontrolled by heat exchange with the temperature control medium flowingin the conduit. In addition, a plurality of elevating pins (not shown)used when transferring the wafer W is provided at the mounting table 41.The elevating pins can project and retract with respect to the mountingsurface for the wafer.

An exhaust gas that has reached a gas exhaust space 68 from a substrateprocessing space S is uniformly discharged and exhausted by a gasexhaust unit 47.

Gas supply sources 210 and 211 are provided at the outside of theprocessing chamber 40 and configured to supply desired gases such as afluorine-containing gas, a hydrogen-containing gas (e.g., NH₃), and adilution gas, e.g., Ar gas, N₂ gas or the like, into the processingchamber 40. The gas supply source 210 introduces a gas into the plasmageneration space P through a gas inlet line 42 a. The gas supply source211 introduces a gas into the substrate processing space S through a gasinlet line 42 b.

In the etching process of the present embodiment, the wafer W is etchedmainly by radicals in the plasma and, thus, it is important to make theradicals uniformly reach the wafer W. However, when a certain gas suchas NH₃ gas becomes radicals, the amount of etchant may be decreased. Inother words, in order to etch an oxide film, NH₄F needs to be generatedand adsorbed onto the wafer. However, if the NH₃ gas is turned into aplasma, NH₄F is not generated. In that case, it is preferable tointroduce a gas into the substrate processing space S while preventingthe gas from being turned into a plasma. Therefore, such a gas isintroduced into the substrate processing space S through the gas inletline 42 b from the gas supply source 211, without being introduced intothe plasma generation space S, so that it is not turned into a plasma.In other words, it is selected whether to introduce a gas into theplasma generation space or into the substrate processing space dependingon types of films to be etched or types of gases to be used.

As described above, in the radical processing apparatus 5 of the presentembodiment, it is possible to select, depending on types of gases,whether to introduce a gas into only the plasma generation space P orboth of the plasma generation space P and the substrate processing spaceS.

The elevation unit 45 is provided at the outside of the processingchamber 40. The elevation unit 45 includes an actuator 81 capable ofvertically moving the mounting table 41 and a driving shaft 82 thatextends from the actuator 81 through the bellows 84.

The gas exhaust unit 47 includes: a gas exhaust line 101 connected to agas exhaust port (not shown) formed in a bottom portion of theprocessing chamber 40; an automatic pressure control valve (APC) 102,provided at the gas exhaust line 101, for controlling a pressure in theprocessing chamber 40; and a vacuum pump 103 for exhausting theprocessing chamber 40.

(Partition Plate)

Provided in the processing chamber 40 is a partition plate 220 fordividing an inner space of the processing chamber 40 into the plasmageneration space P and the substrate processing space S. The plasmageneration space P is a space where a plasma is generated. The substrateprocessing space S is a space where the wafer W is processed. Thepartition plate 220 includes at least two plate-shaped members 230 and231. The two plate-shaped members 230 and 231 are superposed in adirection from the plasma generation space P toward the substrateprocessing space S. A spacer 232 for maintaining a distance between theplate-shaped members 230 and 231 at a predetermined level is providedbetween the plate-shaped members 230 and 231. The plate-shaped members230 and 231 respectively have a plurality of slits 230 a and 231 apenetrating therethrough in the superposing direction. The slits 230 aand 231 a may be through holes. The slits 230 a formed in theplate-shaped member 230 are not overlapped with the slits 231 a formedin the other plate-shaped member 231 when viewed from the superposingdirection. The slits 230 a and 231 a may be formed in a matrix shape inthe plate-shaped members 230 and 231, respectively. In that case aswell, the slits 230 a formed in the plate-shaped member 230 are notoverlapped with the slits 231 a formed in the other plate-shaped member231 when viewed from the superposing direction.

The plate-shaped members 230 and 231 are made of, e.g., quartz glass.The spacer 232 is preferably made of, e.g., quartz. However, the spacer232 may be made of aluminum (Al) or silicon (Si). The partition plate220 which partitions between the plasma generation space P and thesubstrate processing space S functions as a so-called ion trap forsuppressing passage of ions and vacuum ultraviolet light. Accordingly,the number of ions in the substrate processing space S is reduced, whichmakes it possible to reduce damages caused by collision between the ionsand the wafer W.

(Antenna)

The radical processing apparatus 5 of the present embodiment isconfigured as an inductively coupled plasma etching apparatus using aplanar coil type RF antenna. Hereinafter, components related to plasmageneration in the inductively coupled plasma etching apparatus will bedescribed.

The cover 52 serving as the ceiling portion of the processing chamber 40is separated from the mounting table 41 by a comparatively largedistance. The cover 52 is, e.g., a circular quartz plate, and serves asa dielectric window. An antenna chamber 156 where an annular RF antenna154 for generating an inductively coupled plasma in the processingchamber 40 is accommodated while being electromagnetically shielded fromthe outside is provided, as one unit with the processing chamber 40, onthe cover 52.

An annular floating coil 160 having a variable capacitor 158 which canbe coupled with the RF antenna 154 by electromagnetic induction isprovided in a spiral shape inside the antenna chamber 156 in order tovariably control density distribution of the inductively coupled plasmagenerated in a processing space in the processing chamber 40 in adiametric direction.

A high frequency power feed unit 162 includes a high frequency powersupply 164, a matching unit 166, a high frequency power feed line 168,and a return line 170. The high frequency power feed line 168electrically connects an output terminal of the matching unit 166 and anRF input terminal of the RF antenna 154. The return line 170 is an earthline of a ground potential and electrically connects an RF outputterminal of the RF antenna 154 and a ground potential member (e.g., theprocessing chamber 40 or another member) electrically maintained at aground potential.

The high frequency power supply 164 is configured to output a highfrequency power of a predetermined frequency (generally 13.56 MHz orabove) suitable for generation of plasma by inductively coupled highfrequency discharge at a variable power. Accordingly, the high frequencypower supply 164 supplies energy of the predetermined high frequencyinto the processing chamber 40. The matching unit 166 has areactance-variable matching circuit for performing matching between animpedance of the high frequency power supply 164 side and an impedanceof a load (mainly, RF antenna, plasma) side. The capacitance of thevariable capacitor 158 is varied within a predetermined range by acapacitance varying unit 182 under the control of the control unit 90.

The control unit 90 includes, e.g., a microcomputer, and controls theoperations of the respective components of the radical processingapparatus 5, e.g., the gas exhaust unit 47 (the vacuum pump 103), thehigh frequency power supply 164, the matching unit 166, the gas supplysource 210, the gas supply source 211, the capacitance varying unit 182,the chiller unit, the heat transfer gas supply unit and the like, andthe operation (sequence) of the entire apparatus.

The control unit 90 includes a CPU, a ROM (Read Only Memory), and a RAM(Random Access Memory). The control unit 90 controls the temperatureadjustment or the etching process for the wafer W based on the sequenceset in the recipe stored in the RAM or the like. The function of thecontrol unit 90 may be realized by using software or by using hardware.

In the radical processing apparatus 5 of the present embodiment, inorder to generate an inductively coupled plasma and perform etching,first, the gate valve is opened and a wafer W as a processing target isloaded into the processing chamber 40 and mounted on the mounting table41. Then, the gate valve is closed and etching gases are supplied fromthe gas supply sources 210 and 211 and introduced into the processingchamber 40 at predetermined flow rates and a predetermined flow rateratio through the gas inlet lines 42 a and 42 b. A pressure in theprocessing chamber 40 is controlled to a set level by the gas exhaustunit 47. A high frequency power for plasma generation is outputted at apredetermined RF power by switching on the high frequency power 164 ofthe high frequency feed unit 162. Accordingly, a high frequency currentis supplied to the RF antenna 154 through the matching unit 166, thehigh frequency feed line 168, and the return line 170.

When an electrostatic chuck is provided at the mounting table 41, a heattransfer gas (He gas) is supplied to a contact interface between theelectrostatic chuck and the wafer W and confined in the contactinterface by electrostatic attraction force of the electrostatic chuck.Accordingly, the wafer W can be held on the mounting table 41 and a heattransfer effect on the backside of the wafer can be increased.

The etching gas from the gas inlet line 42 a is introduced into theplasma generation space P in the processing chamber 40. Magnetic forcelines (magnetic flux) generated by a high frequency current flowing in acoil segment of the RF antenna 154 and an induced current flowing in thefloating coil 160 penetrate through the cover 52 and traverse the plasmageneration space P in the processing chamber 40. Accordingly, an inducedmagnetic field is generated in an azimuth direction in the processingspace. Ionization collision occurs between electrons accelerated in theazimuth direction by the induced electromagnetic field and molecules oratoms of the etching gas. As a result, a doughnut-shaped plasma isgenerated.

Radicals or ions in the doughnut-shaped plasma are diffused in alldirections in a wide processing space. The radicals isotopically movedown from the plasma generation space P toward the substrate processingspace S while penetrating through the partition plate 220, therebycontributing to the etching of the wafer. On the other hand, the ionsare trapped by the partition plate 220 and prevented from reaching thesurface of the wafer. Accordingly, the etching of the wafer W by theradicals can be promoted.

The “doughnut-shaped plasma” is not limited to a ring-shaped plasma thatis generated only at a diametrically outer side and not generated at adiametrically inner side (central portion) of the processing chamber 40.The “doughnut-shaped plasma” indicates that a volume or a density of aplasma is greater at the diametrically outer side than at thediametrically inner side of the processing chamber 40. The“doughnut-shaped plasma” may not be generated depending on conditionssuch as types of gases used as the processing gases, a pressure in theprocessing chamber 40, and the like.

(Processing Operations of Radical Processing Apparatus)

Hereinafter, processing operations of the radical processing apparatus 5configured as described above will be described. First, in a state wherethe mounting table 41 is lowered by the actuator 81 through the drivingshaft 82, the gate valve is opened and the wafer W is loaded into theprocessing chamber 40 and mounted on the mounting table 41.

Then, the mounting table 41 is raised by driving the actuator 81, sothat a desired substrate processing space S is formed.

Next, a fluorine-containing gas, a hydrogen-containing gas (e.g., NH₃),and an inert gas such as N₂ gas, Ar gas or the like are introduced fromthe gas supply sources 210 and 211, and a plasma is generated from thegases by the energy of the high frequency power outputted from the highfrequency power supply 164. The SiO₂ film on the surface of the wafer Wis subjected to the radical processing mainly by the radials of thegenerated plasma. In the radical processing, the fluorine-containinggas, the hydrogen-containing gas (e.g., NH₃), and the SiO₂ film formedon the surface of the wafer W react with each other to generate AFS thatcan be decomposed by heat.

Upon completion of the radical processing, the mounting table 41 islowered by the actuator 81 of the elevation unit 45. Then, the gatevalve is opened so that the processed wafer W can be unloaded.

(Coating using Quartz)

In the radical processing apparatus 5 of the present embodiment, aportion of the inner wall surface of the processing chamber 40 which ispositioned at least above the mounting table 41 is covered by adielectric material having a recombination coefficient of 0.002 or less.The dielectric material that covers the inner wall surface of theprocessing chamber 40 preferably has a recombination coefficient of0.0005 or less.

As for an example of the dielectric material that covers the inner wallsurface of the processing chamber 40, a replaceable liner member 100made of quartz may be used. The partition plate 220 is made of quartz.

Radicals are hardly adsorbed on quartz. A table shown in FIG. 3 showsprobabilities that H radicals, N radicals and O radicals are recombinedon the surface of the component and inactivated (hereinafter, referredto as “recombination probability”). The source of FIG. 3 is H. C. M.Knoops et al., J. Electrochem. Soc., 157(2010), G241-G249.

According to the table, the recombination probability r of the Hradicals on a silica surface of a component is 0.00004±0.00003.

On the other hand, the recombination probability of the H radicals on analumina (Al₂O₃) ceramic surface of a component is 0.0018±0.0003, whichis 45 times greater than that on the silica surface of the component. Inother words, it is 45 times easier for the H radicals to be adsorbedonto the alumina ceramic surface of the component than onto the silicasurface of the component, and the H radicals are more easily inactivatedon the alumina ceramic surface of the component than on the silicasurface of the component.

The recombination probability of the H radicals on an aluminum (Al)surface of a component of is 0.29, which is 160 times greater than thaton the alumina ceramic surface of the component.

The recombination probability of N radicals on a silica surface of acomponent is 0.0003±0.0002. On the other hand, the recombinationprobability of the N radicals on an aluminum (Al) surface of a componentis 0.0018, which is 6 times greater than that on the silica surface ofthe component.

The recombination probability of O radicals on a silica surface of acomponent is 0.0002±0.0001. On the other hand, the recombinationprobability of the O radicals on an aluminum oxide (Al(OH)₃) surface ofa component is 0.0021, which is 10 times greater than that on the silicasurface of the component.

FIG. 4 shows recombination probabilities r of F radicals. The source ofFIG. 4 is P. C. NORDINE and J. D. LEGRANGE, “Heterogeneous fluorine atomrecombination/reaction on several materials of construction”, AIAAJournal, Vol. 14, No. 5(1976), pp. 644-647.

According to the table, the recombination probability of the F radicalson a quartz surface of a component is 0.00016.

On the other hand, the recombination probability of the F radicals on analumina (Al₂O₃) ceramic surface of a component is 0.000064.

The recombination probability of the F radicals on an aluminum (Al)surface of a component is 0.0018, which is several tens to hundreds oftimes greater than that on the quartz surface of the component or on thealumina (Al₂O₃) ceramic surface of the component.

As described above, in the present embodiment, the portion of the innerwall surface of the processing chamber 40 which is positioned at leastabove the mounting table 41 in the lowermost position and the partitionplate 220 provided above the mounting table 41 are covered by quartz.Therefore, a metal such as aluminum or the like is not exposed to theplasma generation space P or the substrate processing space S.Accordingly, the probability of adsorption and recombination of theradicals on the inner wall surface of the processing chamber 40 can bedecreased. In other words, by coating quartz on the inner wall surfaceof the processing chamber 40 and by using the partition plate 220 madeof quartz, the adsorption of the radicals onto the partition plate 220or the inner wall can be made difficult until the radicals reach thewafer W. As a consequence, it is possible to suppress the inactivationof radicals, improve a decrease in the etching rate especially at theouter peripheral side of the wafer W which is close to the inner wall,and increase in-plane uniformity of the etching rate. Although theportion of the inner wall surface of the processing chamber 40 which ispositioned above at least the mounting table 41 in the lowermostposition and the partition plate 220 provided above the mounting table41 may be covered by alumina instead of quartz, it is more preferable touse quartz capable of suppressing inactivation of radicals.

Therefore, in the radical processing apparatus 5 of the presentembodiment, a distance Wd from the outer peripheral portion of the waferW mounted on the mounting table 41 to the inner wall of the processingchamber 40 may be 10 mm or above, as shown in FIG. 2. In other words,the inactivation of radicals may not be considered and, thus, thedistance from the outer peripheral portion of the wafer to the innerwall of the processing chamber 40 can be shortened. Accordingly, thevolume of the processing chamber can be minimized.

In the present embodiment, quartz is used as the dielectric materialthat covers the inner wall surface of the processing chamber 40.However, the dielectric material is not limited to quartz. For example,the dielectric material that covers the inner wall surface of theprocessing chamber 40 may be a dielectric material having arecombination coefficient of 0.002 or less. In the case of using thedielectric material having a recombination efficient of 0.002 or less,it is possible to suppress inactivation of radicals until the radicalsreach the wafer W, improve the decrease in the etching rate at the outerperipheral side of the wafer W, and improve the in-plane uniformity ofthe etching rate of the wafer W. For example, the dielectric materialthat covers the inner wall surface of the processing chamber 40 may beselected among silicon oxide (SiO_(x)), silicon nitride (SiN), siliconcarbide (SiC), alumina (Al₂O₃) ceramic, and sapphire.

If a film of the dielectric film is formed by spraying on the inner wallsurface of the processing chamber 40, a surface area is increased due toirregularities on the surface. Therefore, the radicals are easilyinactivated on the inner wall surface. Accordingly, it is preferable toform the dielectric film that covers the inner wall of the processingchamber 40 by a method other than spraying.

The dielectric material that covers the inner wall surface of theprocessing chamber 40 is limited to a plasma-resistant material thatdoes not cause metal contamination due to particles. In other words, thedielectric material that covers the inner wall surface of the processingchamber 40 needs to suppress inactivation of the radicals and have highplasma resistance. Further, the dielectric material that covers theinner wall surface of the processing chamber 40 needs to be nonreactiveto the radicals.

The partition plate 220 is made of quartz. However, any material may beused as long as it is a dielectric material having a recombinationcoefficient of 0.002 or less. The surface of the partition plate 220 maybe coated by a dielectric material having a recombination coefficient of0.002 or less.

(Examples of Effect)

FIGS. 5A and 5B show examples of an etching result of SiN in the case ofusing the radical processing apparatus 5 of the present embodiment andan etching result of SiN in the comparative example. In FIG. 5A, thegraph (a-1) shows an etching rate obtained when the inner wall of theprocessing chamber 40 is covered by aluminum (comparative example) andthe graph (a-2) shows an etching rate obtained when the inner wall ofthe processing chamber 40 is covered by quartz (present embodiment). Thehorizontal axis represents a position in a diametric direction of thewafer W, and the vertical axis represents an etching rate.

As a result, the uniformity of the etching rate in the diametricaldirection of the wafer W is higher when the inner wall of the processingchamber 40 is covered by quartz (graph (a-2)) than when the inner wallof the processing chamber 40 is covered by aluminum (graph (a-1)). Fromthe above, it is clear that the radical processing apparatus 5 of thepresent embodiment can achieve the uniformity of the etching rate andpromote the etching by covering quartz that hardly inactivates radicalson the inner wall surface of the processing chamber 40.

As shown in FIG. 2, in the radical processing apparatus 5 of the presentembodiment, an inner wall surface (the bottom surface of the cover 52)52 a of the ceiling portion of the processing chamber 40 is flat.Therefore, the plasma generation space P can have a diameter of 321 mm,as can be seen from the graph (b-2) of FIG. 5B.

On the other hand, when a stepped portion is formed at an outerperipheral side of the inner wall surface 52 a (comparative example),the diameter of the plasma generation space P becomes smaller than 321mm. For example, as can be seen from the graph (b-1) of FIG. 5B, thediameter of the plasma generation space P becomes 284 mm due to thestepped portion formed at the outer peripheral side of the inner wallsurface 52 a.

The graphs (b-1) and (b-2) of FIG. 5B show that when the diffusion ofthe radicals are disturbed by the stepped portion formed at the innerwall surface 52 a, the etching rate is decreased and the uniformitydeteriorates. On the other hand, in the radical processing apparatus 5of the present embodiment, the inner wall surface 52 a is flat, so thatthe decrease in the etching rate and the deterioration of the uniformitycan be improved.

(Other Applications)

The present disclosure may be variously modified without being limitedto the above embodiments. For example, although the above embodimentshave described the example in which the wafer W as a target object isprocessed one by one, the present disclosure may be applied to asubstrate processing system 1 for processing two wafers at a time in theradical processing apparatus 5 and the PHT processing apparatus 4. Or,the present disclosure may be applied to a substrate processing system 1for processing three or more wafers at a time in the radical processingapparatus 5 and the PHT processing apparatus 4.

As described above, in the radical processing apparatus 5 of the presentembodiment, the distance Wd from the outer peripheral portion of thewafer W to the inner wall of the processing chamber 40 can be minimizedto 10 mm by covering quartz that suppresses inactivation of radicals onthe inner wall surface of the processing chamber 40. Therefore, in theradical processing apparatus 5 for processing a plurality of wafers, themounting position of the wafer W can become closer to the inner wallcompared to that in the conventional case, and a degree of freedom indesign can be increased.

The above embodiments have described the example in which the presentdisclosure is applied to the radical processing. However, the presentdisclosure may also be applied to other processes using a gas, e.g., afilm forming process using CVD (Chemical Vapor Deposition) or the like.

In the above embodiment, the gases are introduced from the sidewall ofthe processing chamber 40 through the gas inlet lines 42 a and 42 b.However, the gases may be introduced in a shower shape from the ceilingportion.

In the above embodiment, the wafer was described as an example of thetarget substrate. However, it is not limited thereto, and varioussubstrates for use in LCD (Liquid Crystal Display), FPD (Flat PanelDisplay) or the like, a photomask, a CD substrate, a printed circuitboard and the like may be used.

While the substrate processing apparatus has been described with respectto the above embodiments, the substrate processing apparatus of thepresent disclosure is not limited to the above embodiments and may bevariously changed and modified within the scope of the presentdisclosure. The features described in the above embodiments may becombined without contradicting each other.

For example, the substrate processing apparatus of the presentdisclosure may be applied not only to an ICP (Inductively CoupledPlasma) etching apparatus but also to other substrate processingapparatuses, such as a substrate processing apparatus using a CCP(Capacitively Coupled Plasma), a substrate processing apparatus using aradial line slot antenna, a HWP (Helicon Wave Plasma) apparatus, an ECR(Electron Cyclotron Resonance Plasma) apparatus, or the like.

While the disclosure has been shown and described with respect to theembodiments, it will be understood by those skilled in the art thatvarious changes and modifications may be made without departing from thescope of the disclosure as defined in the following claims.

What is claimed is:
 1. A radical processing apparatus for processing aplurality of substrates, comprising: a processing chamber having aplasma generation space and a substrate processing space; a plasmagenerator configured to generate a plasma in the plasma generationspace; a substrate support disposed in the substrate processing space; apartition unit disposed between the plasma generation space and thesubstrate processing space and configured to allow radicals to penetratetherethrough while suppressing passage of ions therethrough, thepartition unit including a first plate and a second plate verticallysuperposed each other, the first plate having a plurality of firstslits, the second plate having a plurality of second slits, the firstslits being not vertically overlapped with the second slits, areplaceable quartz liner covering an inner wall surface of theprocessing chamber, a distance between an outer peripheral portion of awafer placed on the substrate support and the inner wall surface of theprocessing chamber being 10 mm or above; and a controller configured tocause: placing a substrate on the substrate support, the substratehaving SiO₂ film; supplying a fluorine-containing gas into the plasmageneration space; generating a plasma from the fluorine-containing gasin the plasma generation space; supplying NH₃ gas into the substrateprocessing space; and etching the SiO₂ film by the radicals and the NH₃gas in the substrate processing space, the radicals being obtained fromthe generated plasma through the partition unit.
 2. The radicalprocessing apparatus of claim 1, wherein a high frequency energy issupplied into the plasma generation space from an antenna chamberprovided at an outer side of a ceiling portion of the processing chamberthrough a dielectric window of the ceiling portion.
 3. The radicalprocessing apparatus of claim 1, wherein an inner wall surface of aceiling portion of the processing chamber is flat, without any steppedportion in the ceiling portion.
 4. A radical processing apparatus,comprising: a chamber having a plasma generation space and a substrateprocessing space; a plasma generator configured to generate a plasma inthe plasma generation space; a substrate support disposed in thesubstrate processing space; a partition unit disposed between the plasmageneration space and the substrate processing space, the partition unitincluding a first plate and a second plate vertically superposed eachother, the first plate having a plurality of first slits, the secondplate having a plurality of second slits, the first slits being notvertically overlapped with the second slits; and a replaceable quartzliner covering an inner wall surface of the chamber, a distance betweenan outer peripheral portion of a wafer placed on the substrate supportand the inner wall surface of the processing chamber being 10 mm orabove.
 5. A radical processing apparatus, comprising: a chamber having aplasma generation space and a substrate processing space; a plasmagenerator configured to generate a plasma in the plasma generationspace; a substrate support disposed in the substrate processing space; apartition unit disposed between the plasma generation space and thesubstrate processing space, the partition unit including a first plateand a second plate vertically superposed each other, the first platehaving a plurality of first slits, the second plate having a pluralityof second slits, the first slits being not vertically overlapped withthe second slits; and a replaceable quartz liner covering an inner wallsurface of the chamber, a distance between an outer peripheral portionof a wafer placed on the substrate support and the inner wall surface ofthe processing chamber being 10 mm or above, wherein an entire innerwall surface of a ceiling portion of the processing chamber is flat,without any stepped portion in the ceiling portion.